1. Field of the Invention
This invention relates to two-wheel manually powered bicycles in general, and more particularly to an improved semi-recumbent bicycle. My prior U.S. Pat. No. 4,925,203 issued May 15, 1990 for a "Semi-recumbent Bicycle with Adjustable Frame" is incorporated herein by reference for both essential and nonessential material.
2. Description of the Prior Art
With a semi-recumbent bicycle, the pedal crank assembly is more forward and upward relative to the seat than that of the pedal crank assembly of more conventional bicycles such as multi-speed racing bicycles and mountain style bicycles where the pedal assembly is essentially vertically downward from the seat. The pedal crank assembly of a semi-recumbent bicycle is also somewhat downward and rearward of that associated with fully recumbent bicycles. With a semi-recumbent bicycle, the rider sits in a high-backed seat in a semi-recumbent position elevated above the rear wheel and steers by way of handlebars originating under the area of the rider's upper legs. The legs of the rider of a semi-recumbent extend forward and somewhat downward from the seat to the pedals, while the legs of the rider of a fully recumbent bicycle extend generally straight forward or in some cases even slightly upward from a high-backed seat to the pedals.
A problem associated with many prior art bicycles is the position of the pedals relative to the seat. This seat-to-pedal relationship is primarily what determines the degree of pedal pushing power a given rider can develope. Fully recumbent bicycles have a good seat-to-pedal relationship as far as development of power is concerned, but the vertical height at which the rider sits on these bicycles presents significant safety problems, as sitting quite low (forward and downward of the top of the rear wheel) in a fully recumbent bicycle makes it difficult for both the rider and automobile drivers to detect the presence of each other over and around other vehicles. Low visibility can lead to serious accidents. A significant problem with the pedal positions associated with many fully recumbent bicycles, which does not exist with semi-recumbent bicycles, is that with fully recumbents, the rider's legs are normally extending straight out or even slightly upward in front of him with his feet on the pedals, and the effect of gravity is such that the feet, when not in the pushing mode, have a tendency to slip downward and off of the pedals. Although systems which clip or fasten the feet (shoes) to the pedals are known, many feel such shoe-to-pedal fastening systems create more problems than they solve since if one cannot get his feet off of the pedals and to the ground quick enough, one could easily fall and be seriously injured. A semi-recumbent bicycle allows for pushing against a high-backed seat, and therefore the development of high pedal pushing power, without the problem of the feet sliding downward off of the pedals, and this being due to the angle of approach of the rider's legs and feet to the pedals.
The high power which can be applied by pushing on the pedals with a fully recumbent or semi-recumbent bicycle is dependant on high-backed seats which the rider can push against, in combination with the pedals being of the proper distance from the seat back for the particular rider's leg length. If the pedals are too far from or too close to the seat back for a particular rider's leg length, significant pushing power can be lost, and therefore proper seat positioning (distance) relative to the pedals is important for the development of power.
Seat re-positioning or fine tuning of the positioning thereof for a particular rider is not a significant problem in fully recumbent bicycles since in most cases adjustments to the seat position relative to the pedals simply involves sliding the seat one way or the other horizontally on a horizontally disposed main frame member of the bicycle to either position the seat closer or further from the pedals.
Proper seat positioning on semi-recumbent bicycles is somewhat more difficult than with fully recumbents, as with semi-recumbents the seat adjustment is ideally provided with both vertical and horizontal adjustments to the seat relative to the pedals. With a semi-recumbent which relies on the angle of approach of the rider's legs and feet to the pedals to help maintain his feet on the pedals when not in the pushing mode, if the seat were to be re-positioned straight rearward only, or straight upward only, the angle of approach of the rider's legs and feet to the pedals would be changed, and although this angular change in some instances is insignificant and maybe even desirable, in some situations it is significant and undesirable, and therefore ideally, the rider is given a choice of mixing vertical and horizontal seat adjustments.
Although a structural solution to such seat adjustments for a semi-recumbent is disclosed in my U.S. Pat. No. 4,925,203, that which is taught in my patent is a frame for a semi-recumbent which requires a relatively high step-over for the rider to mount or dismount the bicycle. The frame of my bicycle of the reference patent allows for simple seat position adjustments, wherein independent vertical and horizontal adjustments to the seat position relative to the pedals may be accomplished. The frame disclosed in my prior patent includes a steeply angled, but otherwise straight top tube which attaches at the forward end thereof to the head tube, and then extends at a steep upward elevation to above the rear wheel. The steeply angled top tube of my prior art bike is telescopic to provide for length adjustment, and has a seat post and seat affixed to the rearward upper end of the top tube. The telescopic nature of the angled top tube allows for horizontal positioning the seat closer or further from the pedals, and due to the angled nature of the top tube, lengthening or shortening the top tube also changes the vertical height of the seat. The vertically positioned seat post of my prior art bike is releasibly retained in a clamp which allows for vertical adjustments of the seat position independent of the horizontal adjustment provided by the telescopic top tube. The semi-recumbent bicycle of my previous patent additionally includes an elongated steering stem extending from the upper end of the head tube rearward in general parallel alignment with the steeply angled top tube to support U-shaped handlebars. With the semi-recumbent bicycle of the reference patent, the steering stem extends rearward toward the seat underneath and between the rider's legs, with the wide upwardly turned U-shaped handlebars extending upward around the rider's legs, one portion or arm of the handlebars being positioned on the exterior side of each of the rider's legs. The steering stem is positioned above the angled top tube, and due to the position, and straight but steeply angled structure of this top tube, the steering stem is required for clearance purposes to be positioned relatively high above the ground and thereby requires the rider to straddle what is a relatively high steering stem to mount or dismount the bicycle. Riders having long legs have little problem mounting a given size bicycle of my previous patent, however riders having short legs may have some difficulty with the same size bicycle.
In order to mount a semi-recumbent bicycle such as that of my previous patent, and also the improved semi-recumbent bicycle of this disclosure for that matter, the rider first straddles the elongated steering stem with one leg on each side thereof, which if the steering stem is too high relative to the rider's leg length and thus crotch, is difficult and can be painful. The rider is positioned with his feet on the ground and is facing forward toward the front of the bike. The rider holds the bike stable by holding the handlebars with both hands, as one end portion of the handlebars is positioned on each side of the rider's upper body. The seat of the bike is positioned directly behind and slightly above the rider's buttocks at this point. One pedal crank with pedal is rotated downward (preferably earlier in the procedure), and the rider places one foot on this downward pedal while stabilizing himself and the bike with the other foot still on the ground. The rider then pushes with his other foot against the ground to begin the bike rolling forward, at which time the foot resting on the pedal is pushed against so as to use the low pedal as a step as the rider lifts his other foot from the ground and lifts himself relative to the bike seat directly behind him. The rider moves his buttocks toward and first upward and then downward into the seat as the bike continues to slowly roll, and places the other foot against the opposite pedal to begin pedaling and thus riding the bicycle. To dismount the bike, the rider slows the bike and while still holding onto the handlebars, he slides off of the seat to land with one or both feet on the ground and with his legs straddling the steering stem. Hand brakes on the handlebars are convenient during both mounting and dismounting.
In attempting to address the high step-over associated with the semi-recumbent bicycle of my previous U.S. Pat. No. 4,925,203, a relatively small front wheel (16 inch) was used which resulted in lowering the steering stem which the rider had to straddle while mounting or dismounting the bike. Although the small front wheel resulted in lowering the step-over height and thus making a given size bike mountable and dismountable by a larger variety of sizes of riders having different leg lengths, the relatively small front wheel also resulted in new problems which could be eliminated if a larger front wheel could be used. A larger front wheel would give greater speed potential due to lower rolling resistance, and improved handling under most circumstances during riding. Additionally, there is currently a greater number of high quality larger bike tires (20 inch or larger) on the market today from which to choose than there are smaller (16 inch) or smaller tires, since there is relatively little demand for high or professional quality very small bike rims and tires. Most if not all of the available small bike rims and tires are made for children's bicycles, and are usually not of the highest quality.
It is desireable to have a given size of semi-recumbent bicycle fit a variety of riders to reduce the number of bicycle sizes which need to be manufactured and shipped in a commercial operation, and additionally to provide the necessary seat position fine tuning adjustment capabilities as previously mentioned, and further to provide a semi-recumbent bicycle which handles well during riding.